To address the opioid crisis, and with funding from SAMHSA State Targeted Response to the Opioid Crisis Grants, California?s Medication Assisted Treatment Expansion Project will follow after Vermont?s Hub and Spoke model to establish a California Hub and Spoke system (CA H&SS) for capacity expansion in medication-assisted treatment (MAT) for opioid use disorder (OUD), with a focus on buprenorphine in primary care settings. While Vermont?s Hub and Spoke opioid treatment model has demonstrated favorable impacts, patient outcomes can be improved by engaging patients collaboratively in treatment planning for chronic conditions such as OUD. In response to RFA-DA-18-005 (Expanding Medication Assisted Treatment for Opioid Use Disorders in the Context of the SAMHSA Opioid STR Grants, R21/R33), this project will develop and test a patient decision support tool called Patient Decision Aid for Medication-Assisted Treatment (PtDAMAT) for use in the CA H&SS. The PtDA-MAT is designed to (1) improve patient knowledge and involvement and to subsequently improve treatment adherence and outcomes and (2) to support clinicians in informing and communicating with their patients with OUD along a continuum of care. The project will conduct 1 year of R21 to develop and pilot-test the PtDA-MAT to facilitate shared decision making in CA H&SS, followed by 3 years of R33 to assess the effectiveness of the PtDA-MAT in a randomized controlled trial. The aims of the R21 study are: Aim 1. Develop a patient decision aid (PtDA-MAT) by incorporating best available scientific evidence on MAT as well as feedback from patients and clinical providers related to clinical priorities, perceived utility, and acceptability; Aim 2. Conduct pilot testing of the PtDA-MAT in an iterative process guided by an expert panel and involving key stakeholders (e.g., patients, physicians, policymakers) and field-testing. The aim of the R33 study is to test the effectiveness of PtDA-MAT by conducting a stepped-wedge cluster-randomized trial in CA H&SS (stratified by rural vs. non-rural areas) for adults with OUD. Patient outcomes will be tracked by (1) personal assessments (baseline, 3 months, and 6 months): drug use, overdose, healthcare utilization, and (2) clinical and administrative records (over an average of 24 months): drug treatment status and retention, physical and mental health diagnoses, arrest, incarceration, controlled substance use, and mortality. Multilevel models will be applied to test the intervention effects, controlling for possible temporal trends. The patient-centered decision tool we have proposed takes account of patient values and preferences and will incorporate scientific evidence to increase patients? understanding of possible medication risks, benefits, alternatives, and their associated outcomes. The PtDA-MAT is likely to facilitate evidence-based decisions and promote patient-centered care, leading to improved outcomes for MAT for patients with OUD.